1. Field of the Invention
The present invention relates to a viscous fluid type heat generator not exclusively but particularly suitable for being incorporated in an automobile heating system to heat the automobile passenger compartment. The viscous fluid type heat generator in which a viscous fluid is subjected to a shearing action to generate heat that is in turn transmitted to a circulating heat-transfer or heat-exchange fluid in a heat receiving chamber, and is carried by the heat-transfer fluid to a desired heated area, such as a passenger compartment in an automobile. More particularly, the present invention relates to a viscous fluid type heat generator adapted for being used as a supplementary heat source incorporated in an automobile heating system and having such a construction thereof able to regulate heat generation in response to either a change in an environment in which the viscous fluid type heat generator is used or a change in an operating condition of the heat generator, i.e., an operating speed of the viscous fluid type heat generator.
2. Description of the Related Art
Japanese Unexamined Patent Publication (Kokai) No. 2-246823 (JP-A-2-246823) discloses a typical automobile heating system in which a viscous fluid type heat generator, able to generate heat by using a viscous fluid generating heat when it is subjected to shearing action, is incorporated. The viscous fluid type heat generator disclosed in JP-A-2-246823 includes a pair of mutually opposing front and rear housings tightly secured together by appropriate tightening elements, such as through bolts, to define an inner heat generating chamber and a heat receiving chamber arranged adjacently to the heat generating chamber but separated by a partition wall through which the heat is exchanged between the viscous fluid in the heat generating chamber and the water in the heat receiving chamber. The heat generating chamber is formed as a cylindrical chamber having front and rear inner walls.
The heat exchanging water is introduced into the heat receiving chamber through a water inlet port and delivered from the heat receiving chamber toward an external heating system, so that the heat exchanging water is constantly circulated through the heat generator and the external heating system.
A drive shaft is supported in the front housing via anti-friction bearing so as to rotate about a substantially horizontal axis of rotation, and to support thereon a rotor element in such a manner that the rotor element is rotated with the drive shaft within the heat generating chamber. The rotor element has outer surfaces which are face-to-face with the front and rear inner walls of the heat generating chamber and form labyrinth grooves therebetween, and a viscous fluid is supplied into the heat generating chamber so as to fill the labyrinth grooves between the outer surfaces of the rotor element and the wall faces of the heating chamber.
When the drive shaft of the viscous fluid type heat generator incorporated in the automobile heating system is driven by an automobile engine, the rotor element is also rotated within the heat generating chamber so as to apply a shearing action to the viscous fluid held between the wall surfaces of the heat generating chamber and the outer surfaces of the rotor element. Thus, the viscous fluid which typically consists of a polymer material, for example, a silicone oil having a chain molecular structure exhibiting a high viscosity, generates heat due to the shearing action applied thereto. The heat is transmitted from the viscous fluid to the heat exchanging water circulating through the heat receiving chamber. The heat exchanging water carries the heat to the heating circuit of the automobile heating system, and permits the heating circuit to heat or warm the objective heated area of the automobile such as the passenger compartment.
In the above-described viscous fluid type heat generator according to the prior art, there are provided front and rear gaps in the heat generating chamber, formed between the wall surface of the front wall of the heat generating chamber and the front outer surface of the rotor element, and the wall surface of the rear wall of the heat generating chamber and the rear outer surface of the rotor element. Only a small annular gap provided between the outer circumference of the rotor element and a corresponding annular inner wall surface of the heat generating chamber permits the front and rear gaps to fluidly communicate with one another. Thus, the viscous fluid cannot easily move from the front gap to the rear gap and vice versa within the heat generating chamber. Accordingly, a specified portion of the viscous fluid within the heat generating chamber must be constantly subjected to the shearing action by the rotating rotor element to generate heat, and therefore, the physical property of the specified portion of the viscous fluid is degraded for a short period of time with respect to the overall operation time of the heat generator. The degradation in the physical property of the viscous fluid results in a reduction in the heat generating performance of the viscous fluid during the operation of the heat generator.